Over the years I have picked a couple of Mamiya/Sekor AUTO XTLs more as curiosities but both cameras have one thing in common erratic auto exposure. Stripping one camera I discovered that a vertical EE bracket in the mirror box with a serrated gear edge on it skips over a pinion gear it is supposed to mesh that adjusts the aperture (F stop ring) throwing off the exposures. Close examination shows this to be lack of proper tolerance in manufacturing the EE bracket it is not wide enough to securely engage the pinion gear. The bracket is a complicated piece and only its substituion by a corrected replacement will permanently solve the problem. My inquiry is whether Mamiya ever made a substitute bracket for retrofit. It would have been the right thing to do but the camera did not have a long production life (too advanced for its time) and I doubt Mamiya ever bothered with the issue. I guess it was sheer luck whose AUTO XTL functioned properly or did not. Still someone may have a homemade remedy out there to share otherwise it's a nice looking but disfunctional camera. A CLOSER EXAMINATION shows that the upper standoff screw that guides the vertical travel of the EE bracket against the aperture operating pinion gear has its screw hole drilled 1mm farther away from where it ought to be and this ultimately is the cause of EE dysfunction bracket width not withstanding. That 1mm deviance makes all the difference resulting in improper mating of moving parts. It can't be fixed since drilling a new screw hole would place nearly atop the existant one. Lack of manufacturing tolerance (sloppiness) is the culprit. The parts fail to match and cannot be made to do so. It also explains why Mamiya back then had no remedy for it. End.